Reversible place-exchange during film growth: a mechanism for surfactant transport

Meyer, J.; Vegt, H.A. van der; Vrijmoeth, J.; Vlieg, E.; Behm, R. J.

doi:10.1016/0039-6028(96)00609-7

Cited by 37 publications

(34 citation statements)

References 15 publications

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“…Very recently, Meyer et al 7 proposed (amongst other suggestions) a method of determining the ES barrier based on the surface morphology at the onset of nucleation on top of rst{layer islands as seen by scanning tunneling microscopy (STM). In this paper, we provide a more consistent analytical treatment of this problem and derive a formula di erent from the one proposed by Meyer et al.…”

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confidence: 99%

“…If the island morphology is signicantly di erent from the compact one we assumed, the model cannot be applied straightforwardly. Meyer et al 7 suggested that in the case of fractal morphology the island radius can be replaced with the width of fractal arms but this is certainly a very crude approximation. In any case, the barrier obtained from the model as outlined above will underestimate the real barrier of fractal islands because of more frequent attempts by adatoms to hop down the steps.…”

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confidence: 99%

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Determination of step-edge barriers to interlayer transport from surface morphology during the initial stages of homoepitaxial growth

Šmilauer

Harris

1995

Phys. Rev. B

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We use analytic formulae obtained from a simple model of crystal growth by molecular{beam epitaxy to determine step{edge barriers to interlayer transport. The method is based on information about the surface morphology at the onset of nucleation on top of rst{layer islands in the submonolayer coverage regime of homoepitaxial growth. The formulae are tested using kinetic Monte Carlo simulations of a solid{on{solid model and applied to estimate step{edge barriers from scanning{tunneling microscopy data on initial stages of Fe(001), Pt(111), and Ag (111) Nearly thirty years ago, it was found in eld{ion{ microscopy experiments that interlayer transport on some metal surfaces is suppressed by additional activation barriers to hopping over step edges, 1 and such barriers were recently shown to be present on a semiconductor surface as well. 2 The consequences of this Ehrlich{Schwoebel (ES) barrier for growth on vicinal 3;4 and singular 5 surfaces have been theoretically investigated. In particular, study of the e ects of the ES barrier for growth on a singular surface led to new insights into homoepitaxial growth modes 6 as well as into kinetic roughening of growing surfaces. 2 The ES barrier has emerged as a material parameter of an importance comparable to the surface di usion barrier. It is, however, very di cult to determine this quantity experimentally.Very recently, Meyer et al. 7 proposed (amongst other suggestions) a method of determining the ES barrier based on the surface morphology at the onset of nucleation on top of rst{layer islands as seen by scanning tunneling microscopy (STM). In this paper, we provide a more consistent analytical treatment of this problem and derive a formula di erent from the one proposed by Meyer et al.. This formula and its modi cations are tested using kinetic Monte Carlo (KMC) simulations and applied to STM data for Fe/Fe(001), Ag/Ag(111), and Pt/Pt(111) homoepitaxy.We consider a model of the initial stages of homoepitaxy similar to the one proposed by Lewis and Anderson 8 with circular{shaped islands regularly distributed over a perfect singular surface (Fig. 1). Growth is initiated by a ux of atoms incoming to the surface. The adatom density on the surface increases until it reaches a critical value c at a time t=0 when islands of radius r 0 =1 separated by a distance 2L are formed. (Notice that all lengths are given in units of the lattice constant and are accordingly dimensionless.) We assume that the interisland free{adatom density is then well approximated by its steady{state form with weakly time{dependent coefcients (quasi{static approximation 9 ). We will consider relaxing the assumption of an instantaneous steady state later. Each island has an e ective catchment area of radius L with free{adatom ux equal to zero at a distance r=L. Based on these assumptions, the adatom density on the substrate immediately following nucleation is the solution of the di usion equation Dr 2 + F =0 (1) with boundary conditions (cf. Ref. 9, Section 7.4) d =dr r=R(t) = (R(t)) (and thus als...

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confidence: 99%

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confidence: 99%

Determination of step-edge barriers to interlayer transport from surface morphology during the initial stages of homoepitaxial growth

Šmilauer

Harris

1995

Phys. Rev. B

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“…This mechanism closely resembles that predicted earlier for surfactant mediated growth, such as for Sb-mediated Ag(111) homoepitaxy. [41,42] Though we have no direct evidence for that, these exchange processes may involve and be assisted by vacancies or fluctuating pinhole defects in the Ru film covering the alloyed subsurface layer, as predicted previously for vertical surfactant transport. [73,74] The mechanistic information and conclusions are summarized in the Scheme in Figure 5.…”

Section: Resultsmentioning

confidence: 84%

“…If there is a strong tendency for segregation of the guest metals Pd and Pt, these should float up upon annealing and lead to 2D structures identical to those of the original equilibrated surface alloys. Floating of buried metal species had been observed, for example, during surfactant-mediated growth such as Ag homoepitaxy on Sb/ Ag(111) [40][41][42] or during deposition of various metals on Ag, [43][44][45][46][47][48][49][50] Au, [51][52][53] and Cu [49,[54][55][56][57] single crystals. This floating behavior is driven by a negative impurity segregation energy, which includes the lower surface energy of the up-floating material compared to the respective other species as well as the size mismatch between the host metal and the comparably larger impurity metal.…”

Section: Introductionmentioning

confidence: 99%

Segregation and Stability in Surface Alloys: PdxRu1−x/Ru(0001) and PtxRu1−x/Ru(0001)

2011

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The stability of PdRu/Ru(0001) and PtRu/Ru(0001) surface alloys and the tendency for surface segregation of Pd and Pt subsurface guest metals in these surface alloys is studied by scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). Atomic resolution STM imaging and AES measurements reveal that upon overgrowing the surface alloys with a 1-2 monolayer Ru film and subsequent annealing to the temperatures required for initial surface alloy formation, the Ru-covered Pd (Pt) atoms float back to the outermost layer. The lateral distribution of these species is also essentially identical to that of the initial surface alloys, before overgrowth by Ru. In combination, this clearly demonstrates that the surface alloys represent stable surface configurations, metastable only towards entropically favored bulk dissolution, and that there is a distinct driving force for surface segregation of these species. Consequences of these data on the mechanism for surface alloy formation are discussed.

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“…However, smooth layer morphology is not always thermodynamically favorable [1]. In most deposition cases, the atoms deposited during growth move much more easily away from the step edge than towards cross steps since the surface diffusion of adatoms is higher than interlayer diffusion and, as a result, interlayer mass transport is reduced.…”

Section: Introductionmentioning

confidence: 98%

Growth of ultrathin films of cadmium telluride and tellurium as studied by electrochemical atomic force microscopy

Vidu

Stroeve

2006

Journal of Colloid and Interface Science

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Reversible place-exchange during film growth: a mechanism for surfactant transport

Cited by 37 publications

References 15 publications

Determination of step-edge barriers to interlayer transport from surface morphology during the initial stages of homoepitaxial growth

Determination of step-edge barriers to interlayer transport from surface morphology during the initial stages of homoepitaxial growth

Segregation and Stability in Surface Alloys: PdxRu1−x/Ru(0001) and PtxRu1−x/Ru(0001)

Growth of ultrathin films of cadmium telluride and tellurium as studied by electrochemical atomic force microscopy

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